ABERRATIONS
Instructor-
Golam Dastegir Al-Quaderi
Professor
Department of Physics, DU
1
, Aberration
• In image formation, we have so far adopted
the following approximations:
• A. Paraxial Approximation: The incident rays
make small angles with the optical axis i.e. 𝜃 ≈
0 such that sin 𝜃 ≈ 𝜃, cos 𝜃 ≈ 1
𝜃
Thin Lens Paraxial Approximation 2
, Aberration
• The above is used for both thin lenses as well
as for thick lenses:
𝜃
Thick Lens Paraxial
Approximation
• B. Thin Lens Approximation: The thickness of
the lens is small compared to the radii of
curvature of the lens surfaces i.e. 𝑑 ≪ 𝑅𝑖
3
, Aberration
• C. Outside Air Medium: The medium outside the
lens is taken to be air i.e. 𝑛 ≈ 1
• Special Cases: Furthermore, we have used two
special cases:
• C. Spherical Lens: All the surfaces are spherical in
shape.
• .
4
Instructor-
Golam Dastegir Al-Quaderi
Professor
Department of Physics, DU
1
, Aberration
• In image formation, we have so far adopted
the following approximations:
• A. Paraxial Approximation: The incident rays
make small angles with the optical axis i.e. 𝜃 ≈
0 such that sin 𝜃 ≈ 𝜃, cos 𝜃 ≈ 1
𝜃
Thin Lens Paraxial Approximation 2
, Aberration
• The above is used for both thin lenses as well
as for thick lenses:
𝜃
Thick Lens Paraxial
Approximation
• B. Thin Lens Approximation: The thickness of
the lens is small compared to the radii of
curvature of the lens surfaces i.e. 𝑑 ≪ 𝑅𝑖
3
, Aberration
• C. Outside Air Medium: The medium outside the
lens is taken to be air i.e. 𝑛 ≈ 1
• Special Cases: Furthermore, we have used two
special cases:
• C. Spherical Lens: All the surfaces are spherical in
shape.
• .
4
